At least 15 militants were killed in a US drone strike on an insurgent training centre in Pakistan's tribal area near the Afghan border early on Tuesday, security officials said.
The strike hit targets in Ghulam Khan village on the border between Pakistan and Afghanistan, some 15 kilometres north of Miranshah, the main town in North Waziristan tribal district.
"At least 15 militants were killed when US drones fired six missiles on a militant compound and a vehicle," a senior security official said, raising the death toll from eight.
"Militants were using the compound as a training facility," the official said.
A local intelligence official and another security official in Peshawar confirmed the drone attack and toll.
After the attack, militants surrounded the destroyed compound and were searching through the rubble while an excavator dug graves for the dead in a nearby cemetery, local intelligence officials said.
The area is considered a stronghold of Taliban and Al-Qaeda-linked fighters and has seen a dramatic rise in US drone strikes after intelligence claims emerged in October of a Mumbai-style terror plot to launch commando attacks on European cities.
The leadership of the Haqqani network, which is linked to the Taliban and Al-Qaeda, is also based in North Waziristan.
It has been accused of plotting some of the deadliest attacks on US troops in Afghanistan, including a suicide bombing that killed seven CIA operatives at a US base in Khost last December.
The United States considers Pakistan's tribal belt an Al-Qaeda headquarters and the most dangerous place on Earth.
More than 220 people have been killed in over 40 strikes since September 3, heightening tensions with Islamabad over reported US criticism of Pakistan's failure so far to launch a ground offensive in North Waziristan.
The United States does not as a rule confirm drone attacks, but its military and the Central Intelligence Agency operating in Afghanistan are the only forces that deploy the pilotless aircraft in the region.
Officials in Washington say drone strikes are highly effective in the war against Al-Qaeda and its Islamist allies, killing a number of high-value targets, including the Pakistani Taliban's founding father Baitullah Mehsud.
But the policy is unpopular among the Pakistani public, who see military action on Pakistani soil as a breach of national sovereignty.
It has led to reprisals from militant groups who have targeted NATO supply convoys destined for Afghanistan.